Phosphine-borane complexes are compounds which are generally not decomposed in air or water, but easily converted into phosphines by release of borane with an amine and therefore have been used for synthesis of many organic phosphorus compounds as the equivalent to phosphines. For example, the following reaction scheme of a synthesis method of 1,2-bis[(o-anisyl)phenylphosphino]ethane (DIPAMP) as a ligand useful for an asymmetric reduction is described in Heteroatom Chemistry, No. 3, p. 563-575, 1992.

Also, Tetrahedron Letters, No. 40. p. 201-204, 1999 reports that triarylphosphines are synthesized by reaction with aryltriflate in the presence of a palladium catalyst.

As processes for producing phosphine-borane complexes the following processed are reported:    1) a method for obtaining a phosphine-borane complex by reaction of a phosphine oxide in the presence of cerium chloride, sodium borohydride, and lithium aluminum hydride (Journal of the American Chemical Society, No. 107, p. 5301-5303, 1985);    2) a method for obtaining a phosphine-borane complex by reaction of a phosphine oxide in the presence of methyltriflate, lithium aluminum hydride, and a borane-tetrahydrofuran complex (Organic Letters, No. 3, p. 87-90, 2001);    3) a method for obtaining a phosphine-borane complex by reaction of a phosphine as a starting material with a borane-tetrahydrofuran complex (Angewandte Chemie International Edition, No. 18, p. 781-782, 1979);    4) a method for obtaining a phosphine-borane complex by reaction of a chlorophosphine as a starting material with lithium aluminum hydride and a borane-tetrahydrofuran complex (Journal of the American Chemical Society, No. 112, p. 5244-5252, 1990);    5) a method for obtaining a phosphine-borane complex by reaction of a phosphine oxide in the presence of diethylborane (Chemische Berichte, No. 120, p. 1117-1123, 1987); and    6) a method for obtaining a phosphine-borane complex by reaction of a cyclic phosphine oxide in the presence of a borane-dimethylsulfide complex (Journal of the Chemical Society, Perkin Transactions 1, p. 4451-4455, 2000).